BOSTON – A Phase II cystic fibrosis trial terminated by Vertex Pharmaceuticals (VRTX) earlier this year had always been part of the company’s plan since acquiring the drug candidate from Concert Pharmaceuticals.

Earlier reports, which BioSpace shared, pointed to Vertex terminating the trial, but it was not due to any efficacy concerns. The Phase II program listed as terminated on clinicaltrials.gov is the Concert trial, a Vertex spokesperson said. Heather Nichols said the Phase II trial that was terminated in July was being conducted by Concert prior to the acquisition of the drug candidate. Concert had been exploring the use of CTP-656 as a monotherapy for the disease. However, when Vertex bought the drug earlier this year, the Boston-based company only intended to use it in combination with its other drugs in its CF franchise, including Kalydeco and Orkambi. The hope is the addition of CTP-656 will provide CF patients with a once-daily medication, as opposed to the twice-per day treatment Kalydeco patients are currently prescribed.

“Vertex never intended to advance this product as a monotherapy. It was always intended to be used as part of a combination,” Nichols told BioSpace.

Nichols said CTP-656 will continue to be an asset that Vertex uses as the company continues to develop treatments for cystic fibrosis patients. It will not be used as a monotherapy, but in combination with other drugs, she said several time.

CTP-656, was acquired from Concert Pharmaceuticals (CNCE) earlier this year. CTP-656 is an investigational cystic fibrosis transmembrane conductance regulator (CFTR) potentiator designed for use as part of a once-daily drug combination for the CTFR mutation. Vertex handed over $160 million to Concert for the experimental drug. Concert stands to gain an additional $90 million from Vertex if CTP-656 was approved as part of a combination treatment, according to terms of the deal. Nichols said that deal is still in place, despite misinformation that was previously published.

“Vertex’s plan to develop the molecule as a triple combination is still intact and nothing has changed. All the milestone payments are still set in place,” Nichols said.

Vertex has been making headway in its CF program. In July, the company announced positive data from Phase I and Phase II studies of three different triple combination regimens for cystic fibrosis patients with strains that have been hard to treat using current medications on the market. Data from those trials demonstrated the potential to treat the underlying cause of cystic fibrosis in patients who have one F508del mutation and one minimal function mutation (F508del/Min) – one of the most difficult types of CF to treat. The company has accelerated these trials in hopes of gaining regulatory approval and is also looking at other triple combination options, Vertex indicated in July.

The U.S. Food and Drug Administration is set to make a ruling on Vertex’s combination of tezacaftor and Kalydeco by the end of February 2018.